The present invention relates to the grip device of a robot or manipulator for handling a workpiece.
A prior-art grip device installed on a robot or manipulator is of the type which grasps a workpiece with a fixed force. With the prior-art grip device, therefore, the property of the workpiece has sometimes made it difficult to exactly grasp the workpiece. In order to solve the difficulty, the measure of mounting a force sensor on the fingers of the grip device is taken. When it is intended to sensitively control the grip device relative to the workpiece, the grip device must be furnished with a large number of sensors including a pressure sensor, an ultrasonic wave sensor, etc., besides the aforementioned force sensor. Such attachment of the large number of sensors to the fingers of the grip device renders the structure of the grip device itself large and complicated, and might degrade the reliability due to the insufficient management of the sensors.
There is an example wherein the fingers of a grip device are not provided with any sensors and wherein they are constructed of bimorph type piezoelectric elements thereby to afford both a sensor function and an actuator function for a grasping operation. This example is discussed in a literature "Principle of A Piezo-Electric Micro Manipulator" by Umenani in the 8th I. S. I. R. (lnternational Symposium on lndustrial Robot) (1978). The literature reports that the generation of a grasping force of several mgf or so and the detection thereof are possible. An industrial robot, however, requires capabilities of sensitively positioning the fingers of the grip device to the workpiece as stated before and generating a great grasping force. The above grip device cannot satisfactorily demonstrate the capabilities, and cannot be applied to the industrial robot.